There has been proposed an electrostatic atomizer comprising an atomizing electrode, a counter electrode disposed in opposed relation to the atomizing electrode, and a water supplier for supplying water onto the atomizing electrode, wherein a high-voltage is applied between the atomizing electrode and the counter electrode to atomize water held on the atomizing electrode so as to generate charged fine water droplets each having a nanometer size and carrying a large number of electric charges (i.e., nanometer-size charged mist droplets), as disclosed in the following Patent Publication 1.
The nanometer-size charged water droplets have not only a moisturizing effect, but also a deodorizing effect, a sterilization effect on molds and bacteria, and a suppressive effect on propagation thereof, based on active species existing therein in a state of being wrapped with water molecules. The nanometer-size charged water droplets are as small as a manometer in size and thereby exhibit high floatability on air and high dispersion performance. In addition, the active species exist in the nanometer-size charged water droplets in the state of being wrapped with water molecules and thereby exhibit a longer life as compared with active species existing independently in the form of a free radical. Thus, the nanometer-size charged water droplets have a feature of being able to drift in air for a long period of time evenly and broadly so as to provide enhanced moisturizing effect, deodorizing effect, etc.
In the conventional electrostatic atomizer disclosed in the Patent Publication 1, the water supplier for supplying water onto the atomizing electrode comprises a water tank adapted to be filled with water, and a water transport section adapted to transport water stored in the water tank to the atomizing electrode by means of a capillary phenomenon. This type of water supplier requires a user to refill the water tank with water on a regular basis. That is, a user is obliged to spend time and effort for the cumbersome water-refilling operation, which leads to a problem about poor usability. Moreover, in the conventional electrostatic atomizer, if water containing an impurity, such as Ca or Mg, typically tap water, is used as the supply water, the impurity will cause a problem that it reacts with CO2 in air to form a deposit (i.e., reaction product), such as CaCO3 or MgO, on an end of the water transport section, and the deposit blocks the capillarity-based water supply to hinder the generation of nanometer-size charged water droplets.
A technique intended to solve the above problems has been proposed in the following Patent Publication 2. Specifically, the Patent Publication 2 discloses an electrostatic atomizer which comprises a Peltier unit having a cooling section thermally connected to an atomizing electrode to cool the atomizing electrode, wherein water is supplied onto the atomizing electrode by cooling the atomizing electrode using the cooling section to induce condensation of moisture in air, and a high voltage is applied between the atomizing electrode and a counter electrode to electrostatically atomize the water (condensation water) supplied onto the atomizing electrode.
The conventional electrostatic atomizer disclosed in the Patent Publication 2 has a feature of being able to eliminate the need for the aforementioned water-refilling operation, and avoid the formation of the deposit, such as CaCO3 or MgO, because no impurity is contained in water obtained through the condensation.
The conventional electrostatic atomizer disclosed in the Patent Publication 2 is designed to continuously apply a high voltage to the atomizing electrode while continuously supplying water onto the atomizing electrode by continuously cooling the atomizing electrode using the cooling section of the Peltier unit to induce condensation of moisture in air, so that a condensation-water supply process and an electrostatic atomization process are performed in a simultaneous parallel, i.e., concurrent, manner. In this conventional electrostatic atomizer, if the atomizing electrode is cooled down to 0 (zero)° C. or less, moisture in air will be frozen and attached onto the atomizing electrode in the form of frozen water (i.e., ice) which cannot be electrostatically atomized even if a high voltage is applied to the atomizing electrode. That is, the conventional electrostatic atomizer has the need for cooling the atomizing electrode while avoiding freezing of moisture in air. For meeting this requirement, the Peltier unit is designed to keep the atomizing electrode from being cooled down to 0° C. or less. This means that an allowable lower limit of a cooling temperature for the atomizing electrode is a positive value close to 0° C.
Consequently, under a condition that a mist-receiving space targeted for implementation of electrostatic atomization therewithin has a low humidity, a problem will occur that, even if the atomizing electrode is cooled down to a temperature close to 0° C., moisture in air does not reach a saturated state, which precludes condensation water from being produced. Particularly, under a condition that the mist-receiving space has a temperature of 0° C. or more but close to 0° C., even if the atomizing electrode is cooled down to 0° C., a difference between respective temperatures of the mist-receiving space and the atomizing electrode is small, and thereby any condensation water cannot be produced, except that the mist-receiving space has a relatively high humidity.
FIG. 10 is a graph showing an atomizable zone determined by a relationship of a temperature of the mist-receiving space, a humidity of the mist-receiving space and a setup temperature of the atomizing electrode. In FIG. 10, an atomizable zone in the conventional electrostatic atomizer is located above a curve for a setup temperature of 0° C. (i.e., a specific zone on an upper side relative to the thick curve in FIG. 10), and electrostatic atomization can be induced only in the specific region. As seen in FIG. 10, the conventional electrostatic atomizer has a problem that an environment for electrostatic atomization is largely restricted by temperature/humidity conditions in a mist-receiving space targeted for implementation of electrostatic atomization therewithin, to cause difficulty in utilizing the electrostatic atomizer in low-humidity and/or low-temperature environments, i.e., humidity/temperature environments allowing for utilization of the electrostatic atomizer are limited to a narrow range.
[Patent Publication 1] Japanese Patent No. 3260150
[Patent Publication 2] Japanese Unexamined Patent Publication No. 2006-68711